Olfaction, the act of smelling, is as primitive as it is sophisticated. The human sense of smell, although only a fraction as sensitive as most other animals', not only warns us of danger and helps bond babies and mothers, but also allows us to appreciate the finest of wines and perfumes.Chemistry is at the heart of all olfactory perception, a mechanism by which the brain processes a certain type of information.

The chemical theory of olfaction holds that substances emit particles that waft to the olfactory receptors via diffusion and/or convection. Once there, these particles cause chemical reactions that lead to perception of different odors. However, some materials, such as those with high molecular weight, have no odor, while others emit huge quantities of particles that can travel into the sensory organs.

Many organisms have the ability to perceive odor, which requires...